Molding is a process by virtue of which a molded article can be formed from molding material by using a molding system. Various molded articles can be formed by using the molding process, such as an injection molding process. One example of a molded article that can be formed, for example, from polyethylene terephthalate (PET) material is a preform that is capable of being subsequently blown into a beverage container, such as, a bottle and the like.
As an illustration, injection molding of PET material involves heating the PET material (ex. PET pellets or the like) to a homogeneous molten state and injecting, under pressure, the so-melted PET material into a molding cavity defined, at least in part, by a female cavity piece and a male core piece mounted respectively on a cavity plate and a core plate of a mold. The cavity plate and the core plate are urged together and are held together by clamp force, the clamp force being sufficient to keep the cavity and the core pieces together against the pressure of the injected PET material. The molding cavity has a shape that substantially corresponds to a final cold-state shape of the molded article to be molded. The so-injected PET material is then cooled to a temperature sufficient to enable ejection of the so-formed molded article from the mold. When cooled, the molded article shrinks inside of the molding cavity and, as such, when the cavity and core plates are urged apart, the molded article tends to remain associated with the core piece. Thereafter, the molded article can be ejected off of the core piece by use of one or more ejection structure. Ejection structures are known to assist in removing the molded articles from the core halves. Examples of the ejection structures include stripper plates, stripper rings and neck rings, ejector pins, etc.
With reference to FIG. 1, a preform 100 is depicted, the preform 100 being an example of a typical prior art preform. The preform 100 consists of a neck portion 102, a gate portion 106 and a body portion 104 extending between the neck portion 102 and the gate portion 106.
The preform 100 has a number of additional structural features that fulfill one or more functions. For example, within the neck portion 102, there is provided a thread 108. The purpose for the thread 108 is to cooperate with a complementary thread of a closure device (not depicted) to cap the final-shaped container that is produced from the preform 100, such that to maintain a substance (such as a beverage and the like) contained within a final-shaped container produced from the preform 100 (when such a final-shaped container is blow-molded and eventually filled with the substance). Furthermore, the neck portion 102 comprises a support ledge 112. The support ledge 112 performs multiple functions including, but not limited to, cooperating with various handling devices and structures during injection molding and blow molding stages of production of the preform 100 (for example, cooperation with guiding rails) and the final-shaped container from the preform 100 (for example, cooperation with the blow-molding equipment to provide sealing, etc.).
It is generally known to produce the preform 100 and to subsequently blow-mold it into a final shaped container, such as a bottle for a beverage and the like. It can be appreciated from the illustration of FIG. 1, that the body portion 104 and almost substantially the whole of the gate portion 106 are associated with substantially constant wall thickness. It is, however, known in the art to implement preforms having a varying wall thickness.
For example, U.S. Pat. No. 3,690,798 discloses a variable orifice extruder head for extruding parisons whose wall thickness may be varied over the length of the parison. The extruder head comprises a die assembly movable with respect to a fixed mandrel for varying the die assembly orifice. The die assembly is supported by suspension rods from a fixed housing through which the mandrel passes and in relation to which the mandrel is also fixed. The suspension rods are threaded at their upper ends and have spur gears threaded thereon. An internal ring gear engages each of the spur gears in such manner that rotation of the ring gear causes rotation of the spur gears thereby to raise or lower the die assembly.
Japanese patent 59004292 teaches a preform having a varying wall thickness.
U.S. Pat. No. 4,885,197 teaches a plastic preform for forming blow molded plastic containers wherein the inside wall face of the tubular body portion adjacent the bottom structure and extending onto the bottom structure has a plurality of flat faces with terminal portions thereof. Scallop-shaped segments are provided connecting the terminal portions of each flat face to initiate deformation prior to deformation of the flat faces and thereby have an increased rate and degree of orientation.
U.S. Pat. No. 4,649,068 issued to Collette on Mar. 10, 1987 discloses a preform which is injection molded and which is especially intended for use in the blow molding of a container suitable for receiving a hot fill product. Most particularly, the neck finish of the preform, which becomes the neck finish of the resultant blow molded container, is reinforced against axial compression or foreshortening as may occur when the neck finish is heated to a temperature approaching the glass transition temperature of the polyester from which the neck finish is formed. So as to resist deformation of the neck finish, the neck finish is provided on the interior surface (mouth) thereof with a plurality of axially extending, radially inwardly projecting, circumferentially spaced ribs. If the thread means of the neck finish for receiving a closure is of the interrupted type, there will be at least one rib for each thread element.
U.S. Pat. No. 4,005,245 issued to Edwards on Jan. 25, 1977 discloses plastic preforms adapted for telescopic association with a complementary smooth surfaced mandrel such as is used in conventional plastic blow molding machines. More particularly, the present invention contemplates a novel type of plastic preform as herein, which comprises an elongate hollow plastic member, the inner surface of which in the aggregate conforms generally with the shape defined by the smooth peripheral surface of a complementary mandrel. The inner peripheral surface of the hollow plastic member or preform below the rim portion presents a plurality of circumferentially spaced surface portions adapted for initial direct impingement with restricted areas of the peripheral surface of a complementary smooth surfaced mandrel, the spacing between the said surface areas of impingement providing passageways extending generally longitudinally throughout substantially the entire longitudinal extent of the plastic member. The inner rim portion is devoid of such surface areas of impingement for air sealing the preform on the mandrel.
U.S. Pat. No. 5,455,088 issued to Deemer on Oct. 3, 1995 discloses a plastic bottle having a neck portion defining an opening, a generally tubular bottle body portion depending from the neck portion, and an integral bottle bottom structure closing a lowermost end of the bottle body portion including a continuous standing ring circumscribing a central push-up region is blow molded from a preform which includes a generally tubular preform body portion having an outside wall face and an inside wall face and an integral preform bottom structure closing a lowermost end of the preform. The preform body includes a cylindrical thickened portion which upon blowing forms said continuous standing ring. The central push-up region of the plastic bottle is formed from that portion of the preform below the cylindrical thickened portion. The portion of the preform below the cylindrical thickened portion includes features contributing to enhanced bottle bottom strength while minimizing the amount of resin employed in the structure.
U.S. Pat. No. 4,603,831 issued to Krishnakumar et al. on Aug. 5, 1986 discloses a method and apparatus for the forming of a champagne bottom plastic bottle wherein the bottom is reinforced by internal radiating ribs which are formed by solid material. The bottle is formed in the customary manner by utilizing a preform which has molded on the inner surface thereof longitudinal ribs. The preform is formed by conventional injection molding equipment which has been modified only to form along the lower part of the customary core member longitudinally extending rib forming grooves.
U.S. Pat. No. 5,366,774 issued to Pinto et al. on Nov. 22, 1994 discloses a tubular preform for a blow-molded container. The preform has a closed end and an opposite open end, the relative dimensions of the ends being such that the closed end would be receivable in the open end of a similar preform to nest there were it not for the provision of an antinesting feature in the form of a plurality of axially extending ribs which protrude inwardly from the inner surface of the preform adjacent to the open end to prevent entry of another preform.
PCT patent publication 2007/083266 by Pagliacci published on Jul. 26, 2007 discloses a disposable container, of the type wherein at least part of the lateral surface of the container (1) consists of a bellow-shaped structure comprising a plurality of adjacent folds joined by internal (2) and external (3) hinge bands, respectively. At least the internal hinge bands (2) have, in a cross-section, a lobed structure comprising mutually alternate ridges (4) and valleys (5) which are continuously joined, the ridges and the valleys of one of said internal hinge bands (2) being offset, in the projection on a perpendicular plane to the container axis (A), with respect to the ridges and valleys of the immediately surrounding internal hinge bands. In correspondence of said ridges there are further provided shape stiffening areas (6) of the bottle wall. Each of said stiffening areas (6) is joined to the surrounding stiffening areas by slanting ribs (8).